Mechanism for controlling the intermittent forward movement of a workpiece support



Jan. 4, 1966 WEGERDT 3 226,

F. MECHANISM FOR CONTROLLING THE INTERMITTENT FORWARD MOVEMENT OF A WORKPIECE SUPPORT Filed Jan. 15, 1965 Jnventor FRITZ WEGERDT by ttorney The invention relates to a mechanism for controlling the advance of the work during the idle stroke of a hydraulically drivenmachine tool, especially a slotting or grinding machine, with a m1 carrier that is moved THE INTER- MOVEMENT OF A WORK- re'ctilinearly back and forth by a piston-and-cylinder motor. h 7

It has been old for example in slotting or grinding machines with rack and-pinion drives to mount the tool on a reciprocating carriage actuated by a cylinder-and piston motor while the workpiece is clamped in a holder that-is advanced by a rotatable member to control the depth of cut. Sometimes this advance is continuous, but in'many cases such continuous advance cannot be used, it being usually necessary to efiect the advance during the idle stroke of the tool. Here certain matters have to be taken into consideration. The extent of the advance may have to be different in different cases. The length of reciprocation of the tool carriage will alsochange, which in turn will change the amount of time that remains available for the idle stroke. This time is also dependent on the velocity of forward movement of the piston-and-cylinder' motor, which is also variable. j

It would be possible to make the adjusting time for the rotatable advancing member so small; regardless of the reciprocation time of the tool carrier, that even with very short and rapid reciprocations the adjustment time will fall entirely within the limits ofthe idle stroke, Such a system, however, is uneconomical and not conducive to long useful life of the machine. p

"'In machine tools with purely mechanical driving systems the above-mentioned problems do not offer serious diificulties because there will always be driving devices conveniently at hand which give an exact picture of the instantaneous settings. p

The primary purpose ofthis invention is to provide a hydraulically operated mechanism in which the rotatable actuated advance of the work-support is accomplished by means of a reciprocating hydraulic piston with adjustable length of stroke.

Other objects and advantages of my invention will become clear to those skilled in the art after a study of the following detailed description, in conection with the accompanying drawing.

This invention solves the above-mentioned problem by providing an auxiliary pump with variable volumetric output for delivering pressure fluid to the work-advancing piston, in combination with a differential adjusting mechanism having at least three input members for regulating the pump. One of the input members is responsive to the stroke-limiting device of the work-advancing piston, the second is responsive to the forward velocity of the reciprocating motor, and the third is responsive to the adjusted length of stroke of the reciprocating motor, all

United States Patent 3,226,936 Patented Jan. 4, 1966 three of these members cooperating to regulate the auxiliary pump through a common control member. The three input members are preferably in the form of three rotatable threaded shafts. One of these shafts is rotatably butnot slidably mounted while each of these shafts is threadedly connected to a slidable but nonrotatable nut member, each nut member having one of the other shafts or the common control member nonslidably coupledto it.

With such a mechanism it is possible to keep the volume of the pressure fluid delivered to the hydraulic advancing piston in unit time strictly proportional to the length of stroke of this work-advancing piston, to the velocity of reciprocation of the hydraulic motor, and to the length of'stroke of the hydraulic motor. In this manner it will members of the differential.

f device 4. Instead of the latter, adjustable throttles in" Preferably the arrangement is such that the input mem-' bers of the diiierential mechanism will be actuated automatic'ally in accordance with the values to which they are responsive. This can be accomplished in various ways. For the automatic introduction of the rotatably actuated work-support advance a screwthreaded member can be used to limit the rectilinear movement in one direction of the work-advancing piston which can be coupled to such member either directly or through intermediate gearing. In a similar manner the contemperaneous speed of the reciprocating motor can be introduced into the differential mechanism simultaneously. If the velocity of the work-advancing piston is controlled by a throttle valve, the adjustment of such a valve can be delivered to one of the threaded input shafts of the differential. If a pump with variable output is used to actuate that piston, the adjusting mechanism of the pump can be used for delivering the speed of the piston to one of the input Finally in order to deliver the length of stroke of the reciprocating piston motor to the differential, the distance between the cams for reversing the movement of the reciprocating motor can be used. To introduce this distance into the diiferential, one of these cams can carry a toothed rack with which a pinion carried by the other cam is in mesh, the rotation of the pinion being then delivered to one of the threaded shafts of the differential. It would also be possible to use a voltage-responsive electric motor for rotating that shaft, in which case the motor would be connected to a potentiometer bridging the space between the two cams.

The invention is further illustrated by the schematic drawing showing one example thereof in a cross-sectional view.

In the drawing the tool-supporting carriage 1 is moved in either direction by a reciprocating hydraulic motor 2 whose piston extends through both ends of the cylinder for linear reciprocation. The motor 2 is actuated by hydraulic fluid from a hydrostatic main pump 3 with volumetric adjustability. In the example shown the pump is of radial piston type with a raceway that is adjustable across the Zero position. Adjustment for the required volumetric output is provided for by a screwthreaded conduits 5 and 6 could be used. Reversal of the direction of movement of motor 2 is effected in the usual manner by a transposable valve 7 that is actuated by feelers 8 and s 9 of known construction for actuating said valve, the feelers being actuated by cams 10 and 11 which, as shown diagrammatically at 12, are connected to the reciprocating piston motor 2 or tool carriage 1 for movement in unison with the latter. The distance between the cams and their setting relative to the carriage 1 is adjustable.

To advance the work-holder (not shown), the piston 15 is provided with rack teeth 16 for rotating a gear 17 on a shaft connected to the work-holder. The length of stroke of the piston and therefore the forward movement of the work are controlled by a threaded bolt 18 serving as an abutment for the piston 15. The position of the bolt 18 can be controlled by the rotatable but longitudinally immovable nut 19.

For actuating the piston 15 an auxiliary pump 20 is provided with variable volumetric output. In the example shown the pump 20 is of the radial piston type with an arcuately adjustable raceway. The conduit 21 of this pump can be selectively connected to either side of the piston 15 by valve 22. The reversal is also dependent on the action of cams 10 and 11. Further details are not shown, because such devices are old. The driving of the rotatable member to control the advance of the workpiece can also be effected by means of a one-way clutch so that the work-support will not be moved during the return movement of the piston 15.

The length of strike of the piston 15 determines only the distance advanced by the work-support. .On the other hand the time during which such advance occurs is determined by the volumetric output of the pump 20. In order that the time of advance will always remain adjusted to the idle stroke time of the motor 2 and to the extent of forward movement, a differential adjusting mechanism 25 is provided. This comprises three parallel adjusting shafts 26, 27 and 28. The shaft 27 is not movable longitudinally in the housing 29 but is threaded into a longitudinally slidable nut 30 which is connected through an extension 31 to a shaft 26 so that these parts will move together longitudinally. The shaft 26 is in threaded engagement with a movable nut 32 which is connected to the shaft 28 for longitudinal movement in unison therewith. The shaft 28 is screwed into a sled 33 connected to the raceway of the pump 20. The result will be that the rotation of any one of the threaded shafts will cause movement of the sled 33 and thereby effect regulation of the pump 20. The shafts 26 and 28 can be shifted manually from any of their adjusted positions by rotation of the handwheel 35. Preferably, however, their shifting is accomplished automatically by connecting the shaft 28 by a chain-and-sprocket drive to a sprocket wheel 41 on the rotatable nut 19 so that every adjustment of the abutment bolt 18 is transferred proportionately to the shaft 28. Obviously there could also be interposed a change speed gearing.

In a similar manner the shaft 26 is connected by a chain-and-sprocket drive 42 to the threaded shaft 43 of the adjusting mechanism 4 of the main pump 3. Each adjustment of the pump 3 therefore corresponds to a certain adjustment of the movable nut 32 on the shaft 26.

The automatic introduction of the appropriate length of stroke of the motor 2 can be accomplished in various ways. In the example shown, the distance between the cams 10 and 11 is fed into shaft 27. For this purpose cam 10 can carry a potentiometer winding whose ends 51 and 52 are connected across a source of electric current 53. Cam 11 carries a movable contact 54 taking current from the potentiometer at an intermediate point. At terminals 55 a voltage which is proportional to the distance between the cams will therefore be taken from the potentiometer and will be delivered at 56 to a suitable adjusting motor 57 whose shaft 58 is connected with the threaded shaft 27.

The two cams can, however, also carry a toothed rack and a pinion meshing therewith and connected to the shaft 27' to which the movement of the pinion is transmitted. In both cases the position of the slidable nut 30 on the threaded shaft 2'7 corresponds exactly to the distance between the cams 10 and 11 and therefore also to the length of stroke of the piston motor 2.

All three of these conditions which are delivered to the differential mechanism 25 will be transmitted to the adjusting member 34 so that the pump 20 at every instant will deliver pressure fluid to the piston 15 at a rate determined by the sum or differential effect of these three values.

While the above invention has been fully described it is to be understood that it is not limited to the embodiment shown, and that various changes may be made therein by those skilled in the art without departing from the spirit of this invention;

What is claimed is:

1. A mechanism for controlling the intermittent for- Ward movement of a workpiece support during the idle stroke of a hydraulically driven machine tool of the slotting or grinding type having a reciprocating tool-carrier actuated by a reciprocating piston motor and a hydraulic work-advancing piston with adjustable stroke length comprising an auxiliary pump of variable output, a differential mechanism with at least three input members, the first of said input members responsive to the length of the stroke of said work advancing piston, the second of said input members responsive to the speed of said reciprocating motor, the third of said input members responsive to the adjusted length of stroke of the reciprocating motor, said differential mechanism controlling said auxiliary pump, a pump regulating member to control the output of said auxiliary pump and means to control said work advancing piston by pressure fluid from said auxiliary pump. a

2. A mechanism for controlling the intermittent forward movement of a workpiece as claimed in claim 1 in which the input members of the differential mechanism comprise three parallel threaded. shafts of which one is longitudinally shiftable and each of them is threadedly positioned in a nut member which is slidably non-rotatably guided, said nut member being nonshiftably coupled to one of the other shafts.

3. A mechanism for controlling the intermittent forward movement of a workpiece as claimed in claim 1 in which the input members of the differential mechanism comprise three parallel threaded shafts of which one is longitudinally shiftable and each of them is threadedly positioned in a nut member which is slidably non-rotatably guided, said nut member being nonshiftably coupled to the pump-regulating member.

4. A mechanism for controlling the intermittent forward movement of a workpiece as claimed in claim 1 and means to actuate said input members of the differential mechanism automatically by the conditions to which they are responsive.

5. A mechanism for controlling the intermittent forward movement of a workpiece as claimed in claim 1, a chain-and-sprocket gearing to the differential and means to deliver the length of stroke of the work-advancing piston by said chain and sprocket gearing to the differential.

6. A mechanism for controlling the intermittent forward movement of a workpiece as claimed in claim 1, a

' device responsive to the rate at which the pressure fluid is delivered to the reciprocating motor and means to deliver the speed of the reciprocating motor to said differential mechanism through the rate responsive device.

'7. A mechanism for controlling the intermittent forward movement of a workpiece as claimed in claim 1,

8. A mechanism for controlling the intermittent forward movement of a workpiece as claimed in claim 7, the means responsive to the distance between the cams comprising a toothed rack, connected to one of the cams, a pinion in mesh with the rack, connected to actuate the third input member in response to the rotation of the pinion.

9. A mechanism for controlling the intermittent forward movement of a workpiece as claimed in claim 7, a

potentiometer with sliding contact having its ends con- 10 nected across a voltage source, one end of said potentiometer connected to one of the cams, the sliding contact connected to the other cam, 21 voltage-responsive motor electrically connected to the two cams for actuating the third input member in response to the distance between the cams.

No references cited.

EDGAR W. GEOGHEGAN, Primary Examiner. 

1. A MECHANISM FOR CONTROLLING THE INTERMITTENT FORWARD MOVEMENT OF A WORKPIECE SUPPORT DURING THE IDLE STROKE OF A HYDRAULICALLY DRIVEN MACHINE TOOL OF THE SLOTTING OR GRINDING TYPE HAVING A RECIPROCATING TOOL-CARRIER ACTUATED BY A RECIPROCATING PISTON MOTOR AND A HYDRAULIC WORK-ADVANCING PISTON WITH ADJUSTABLE STROKE LENGTH COMPRISING AN AUXILIARY PUMP OF VARIABLE OUTPUT, A DIFFERENTIAL MECHANISM WITH AT LEAST THREE INPUT MEMBERS, THE FIRST OF SAID INPUT MEMBERS RESPONSIVE TO THE LENGTH OF THE STROKE OF SAID WORK ADVANCING PISTON, THE SECOND OF SAID INPUT MEMBERS RESPONSIVE TO THE SPEED OF SAID RECIPROCATING MOTOR, THE THIRD OF SAID INPUT MEMBERS RESPONSIVE TO THE ADJUSTED LENGTH OF STROKE OF THE RECIPROCATING MOTOR, SAID DIFFERENTIAL MECHANISM CONTROLLING SAID AUXILIARY PUMP, A PUMP REGULATING MEMBER TO CONTROL THE OUTPUT OF SAID AUXILIARY PUMP AND MEANS TO CONTROL SAID WORK ADVANCING PISTON BY PRESSURE FLUID FROM SAID AUXILIARY PUMP. 